Electrochemical Impedance Spectroscopy Study Of Ion-erosion Process Of Cement-based Materials

Cementititous materials and concrete is the most widely used material in construction industry. Deterioration and durability of materials is the key factor for service life of concrete structures. And the materials are often exposed to harmful ions or chemicals material, such as: carbon dioxide, chloride ions, sulfate ions. The corrosion due to harmful substances is related to the internal microstructure performance and properties of the materials. Therefore, the research of the erosion behavior in cementititous materials is necessary. There are many disadvantages of current test methods, like need to destroy, long testing time, susceptible to environment and so on. However, the electrochemical impedance spectroscopy(EIS) is an ondestructive method which is also effective to study the corrosion procedure.EIS can characterize the development and change in the microstructure during ions permeation from microscopic view. Meanwhile, EIS can show the changes of mechanism of the erosion process which is a complex procedure with time. And EIS makes up for the shortcomings that mentioned-above. So, EIS has become an optimized tool to estimate the properties of the cementititous materials and concrete.In present paper, the erosion procedure is characterized and analyzed by electrochemical impedance spectroscopy method, which based on the theory of EIS.A novel equivalent circuit model is established to explain ion erosion behavior of the cementitious materials and successfully proved. The influence of water/cement ratio, and the time dependence on the erosion behavior has been studied. It has been found that the model parameters have direct function related to time and corrosion depth. At last, the prediction of corrosion depth can be obtained by using the function. The main research contents and results as followed:(1)Compare with the equivalent circuit models before, by taking into account the solid/liquid double-phase interaction and Warburg interaction, the new EIS model with RS(Q1(Rct1W1))(Q2(Rct2W2))was proposed and then verify its coherency.(2)In the testing procedure of cement paste, the Nyquist is changing with the corrosion time. Different water/cement ratio can influence the properties of cementititous materials. The model parameter which is Rct1 have direct function related to time and corrosion depth. Then, we can use this functional relationship to predict the corrosion depth.(3)In the testing procedure of cement/ fly ash / slag system, the Nyquist is changing with the corrosion time. Different ratio can influence the properties of cementititous materials. The model parameter Rct1 has direct function related to time and corrosion depth. Then, we can use this functional relationship to predict the corrosion depth.